California energy operator officials say they expect to get by without blackouts. Southern California Edison says it might retire the nuclear plant by year's end.

Early morning surfers catch a few waves as a fog bank clears away at Lower… (Mark Boster, Los Angeles…)

California energy officials are preparing for another summer without the San Onofre power station while facing the growing possibility that the nuclear plant will never return to service.

The nuclear plant, one of only two in the state, was powered down more than a year ago when a small amount of radioactive mist leaked from one of the thousands of tubes in the plant's steam generators.

Southern California Edison officials said in financial statements last week that if federal regulators do not agree to the utility's proposal to restart one of the plant's two units at partial power, they might elect to retire the plant completely by the end of the year.

"There's just a general limit of how much we can continue to rack up these costs without certainty of cost recovery," Edison International Chief Executive Ted Craver told analysts.

So far, the mothballed plant has cost Edison more than half a billion dollars, and the tab continues to grow.

Officials with the California Independent System Operator, which oversees the state's power grid, said Monday they expect to get through another summer without blackouts even if San Onofre remains shuttered — although damaging wildfires in the months ahead could undermine that prediction.

With the plant out of service, the region is more dependent on imported power, and California Independent System Operator Chief Executive Steve Berberich said he was "pretty concerned" that fires could threaten transmission lines in remote areas.

A long-range future without the plant is a more complicated scenario, largely because the state is also implementing new regulations on the way coastal power plants use seawater for cooling. San Onofre will loom large in upcoming discussions on whether to retire, retrofit or repower 11 gas-fired coastal plants that supply about 11,000 megawatts of power — nearly five times what San Onofre generates.

The nuclear plant, which once supplied enough power for about 1.4 million homes in Southern California, has been shuttered for 15 months because of unusual deterioration of tubes in its replacement steam generators.

The plant is now embroiled in a complex web of regulatory processes. The U.S. Nuclear Regulatory Commission is weighing a proposal by Edison to restart the less heavily damaged unit and run it at partial power for five months in hopes that reduced power will eliminate the conditions that led to the wear and help to determine whether the other unit can run again without "extensive repairs."

The company asked the NRC for a decision on the restart plan before June but acknowledged last week that it is unlikely to get one by then.

Meanwhile, the NRC's office of investigations and office of inspector general are probing whether there was wrongdoing by Edison in connection with the steam generator replacement.

Separately, the California Public Utilities Commission is weighing whether to offer refunds to customers because of the plant's extended outage. Hearings in the initial phase of that process — focused on a portion of the plant's costs from last year — begin in San Francisco next week, with a preliminary ruling expected in July.

The commission will look at the $671-million cost of the steam generators and the cost of replacing the plant's power in a later stage.

Matthew Freedman, an attorney with ratepayer advocate group the Utility Reform Network, speculated that Edison might have publicly floated the specter of retiring the plant in an effort to pressure the NRC into acting more quickly or the PUC into agreeing to some sort of settlement on costs if the plant does close.

"Edison's worry is that they would shut down the plant and they would still eat a ton of money," he said.

Freedman said the costs could look "pretty ugly" for ratepayers if the plant limps along with one unit running at partial power, or if the plant closes and Edison is able to recover its investment from customers.

Edison has reported spending $109 million on repairs and inspections and $444 million for replacement power since the plant closed. But the company has not publicly said how much it might cost to make repairs that would allow the plant to run at full power again.